High-efficiency and sustainable photoelectric conversion of CO2 to methanol over CuxO/TNTs catalyst by pulse potential method

Herein, we report a special pulse potential method to increase methanol production and keep the CuxO/TiO2 nanotube array (TNT) catalyst active during photoelectrocatalysis reduction of CO2. The CuO/TNT catalyst was prepared via electrodeposition of copper on anodized titanium oxide followed by heat treatment. The variation of valence of copper in the photoelectrocatalytic reduction process was studied intensively by high-resolution transmission electron microscopy, XPS, and AES characterizations. Results show that the photocatalytically active CuO is apt to be reduced to elementary Cu during photoelectrocatalysis process, leading to rapid decay of photocatalytic activity. While for the case of pulse potential regime, another photocatalytically active oxide, Cu2O, will be produced on the surface during anodic pulse, which can effectively maintain the photocatalytic activity of catalyst. CV study indicates that the oxidation of Cu is prior to the oxidation of methanol, so the methanol oxidation hardly ever happens during anodic pulse stage. The catalyst applied in pulse potential regime provided a much larger photocurrent than that in constant potential regime over an extended period of time. As a result, the yield of methanol produced in optimized pulse potential condition is greatly increased, nearly twice that in constant potential regime.